Immunomodulators

ABSTRACT

In accordance with the present disclosure, macrocyclic compounds have been discovered that bind to PD-L1 and are capable of inhibiting the interaction of PD-L1 with PD-1 and CD80. These macrocyclic compounds exhibit in vitro immunomodulatory efficacy thus making them therapeutic candidates for the treatment of various diseases including cancer and infectious diseases.

CROSS-REFERENCE TO RELATED APPLICATIONS

This PCT application claims the priority benefit of U.S. ProvisionalApplication No. 62/957,383, filed Jan. 6, 2020 which is incorporatedherein by reference in its entirety.

FIELD

The present disclosure provides macrocyclic compounds that bind to PD-L1and are capable of inhibiting the interaction of PD-L1 with PD-1 andCD80. These macrocyclic compounds exhibit in vitro immunomodulatoryefficacy thus making them therapeutic candidates for the treatment ofvarious diseases including cancer and infectious diseases.

BACKGROUND

The protein Programmed Death 1 (PD-1) is an inhibitory member of theCD28 family of receptors, that also includes CD28, CTLA-4, ICOS andBTLA. PD-1 is expressed on activated B cells, T cells, and myeloidcells.

The PD-1 protein is a 55 kDa type I transmembrane protein that is partof the Ig gene superfamily. PD-1 contains a membrane proximalimmunoreceptor tyrosine inhibitory motif (ITIM) and a membrane distaltyrosine-based switch motif. Although structurally similar to CTLA-4,PD-1 lacks the MYPPY motif that is critical for CD80 CD86 (B7-2)binding. Two ligands for PD-1 have been identified, PD-L1 (B7-H1) andPD-L2 (b7-DC). The activation of T cells expressing PD-1 has been shownto be downregulated upon interaction with cells expressing PD-L1 orPD-L2. Both PD-L1 and PD-L2 are B7 protein family members that bind toPD-1, but do not bind to other CD28 family members. The PD-L1 ligand isabundant in a variety of human cancers. The interaction between PD-1 andPD-L1 results in a decrease in tumor infiltrating lymphocytes, adecrease in T-cell receptor mediated proliferation, and immune evasionby the cancerous cells. Immune suppression can be reversed by inhibitingthe local interaction of PD-1 with PD-L1, and the effect is additivewhen the interaction of PD-1 with PD-L2 is blocked as well.

PD-L1 has also been shown to interact with CD80. The interaction ofPD-L1/CD80 on expressing immune cells has been shown to be an inhibitoryone. Blockade of this interaction has been shown to abrogate thisinhibitory interaction.

When PD-1 expressing T cells contact cells expressing its ligands,functional activities in response to antigenic stimuli, includingproliferation, cytokine secretion, and cytotoxicity, are reduced.PD-1/PD-L1 or PD-L2 interactions down regulate immune responses duringresolution of an infection or tumor, or during the development of self.Chronic antigen stimulation, such as that which occurs during tumordisease or chronic infections, results in T cells that express elevatedlevels of PD-1 and are dysfunctional with respect to activity towardsthe chronic antigen. This is termed “T cell exhaustion”. B cells alsodisplay PD-1/PD-ligand suppression and “exhaustion”.

Blockade of PD-1/PD-L1 ligation using antibodies to PD-L1 has been shownto restore and augment T cell activation in many systems. Patients withadvanced cancer benefit from therapy with a monoclonal antibody toPD-L1. Preclinical animal models of tumors and chronic infections haveshown that blockade of the PD-1/PD-L1 pathway by monoclonal antibodiescan enhance an immune response and result in tumor rejection or controlof infection. Antitumor immunotherapy via PD-1/PD-L1 blockade canaugment therapeutic immune response to a number of histologicallydistinct tumors.

Interference with the PD-1/PD-L1 interaction causes enhanced T cellactivity in systems with chronic infection. Blockade of PD-L1 causedimproved viral clearance and restored immunity in mice with chromoiclymphocytic chorio meningitis virus infection. Humanized mice infectedwith HIV-1 show enhanced protection against viremia and viral depletionof CD4+ T cells. Blockade of PD-1/PD-L1 through monoclonal antibodies toPD-L1 can restore in vitro antigen-specific functionality to T cellsfrom HIV patients.

Blockade of the PD-L1/CD80 interaction has also been shown to stimulateimmunity. Immune stimulation resulting from blockade of the PD-L1/CD80interaction has been shown to be enhanced through combination withblockade of further PD-1/PD-L1 or PD-1/PD-L2 interactions.

Alterations in immune cell phenotypes are hypothesized to be animportant factor in septic shock. These include increased levels of PD-1and PD-L1. Cells from septic shock patients with increased levels ofPD-1 and PD-L1 exhibit an increased level of T cell apoptosis.Antibodies directed to PD-L1, can reduce the level of immune cellapoptosis. Furthermore, mice lacking PD-1 expression are more resistantto septic shock symptoms than wildtype mice. Studies have revealed thatblockade of the interactions of PD-L1 using antibodies can suppressinappropriate immune responses and ameliorate disease signs.

In addition to enhancing immunologic responses to chronic antigens,blockade of the PD-1/PD-L1 pathway has also been shown to enhanceresponses to vaccination, including therapeutic vaccination in thecontext of chronic infection.

The PD-1 pathway is a key inhibitory molecule in T cell exhaustion thatarises from chronic antigen stimulation during chronic infections andtumor disease. Blockade of the PD-1/PD-L1 interaction through targetingthe PD-L1 protein has been shown to restore antigen-specific T cellimmune functions in vitro and in vivo, including enhanced responses tovaccination in the setting of tumor or chronic infection. Accordingly,agents that block the interaction of PD-L1 with either PD-1 or CD80 aredesired.

SUMMARY

The present disclosure provides macrocyclic compounds which inhibit thePD-1/PD-L1 and CD80/PD-L1 protein/protein interaction, and are thususeful for the amelioration of various diseases, including cancer andinfectious diseases.

In a first aspect the present disclosure provides a compound of formula(I)

or a pharmaceutically acceptable salt thereof, wherein:

-   -   R^(x) and R^(y) are independently H,

provided that at least one of R^(x) and R^(y) is other than H;

-   -   R¹ is H, halogen or C₁-C₆ alkyl;    -   R² and R³ are independently H, halogen, C₁-C₆ alkyl, or aryl;        said aryl group substituted with 0-3 R^(3a) ;    -   R^(3a) is halogen or COOR⁴;    -   R⁴ is H or C₁-C₆ alkyl; and        R⁹ is H or C₁-C₃ alkyl.

In a first embodiment of the first aspect, the present disclosureprovides a compound of formula (I), or a pharmaceutically acceptablesalt thereof, wherein R^(x) is H.

In a second embodiment of the first aspect, the present disclosureprovides a compound of formula (I), or a pharmaceutically acceptablesalt thereof, wherein R^(y) is H.

In a third embodiment of the first aspect, the present disclosureprovides a compound of formula (I), or a pharmaceutically acceptablesalt thereof, wherein R⁹ is H or —CH₃.

In a fourth embodiment of the first aspect, the present disclosureprovides a compound of formula (I), or a pharmaceutically acceptablesalt thereof, wherein

-   -   R² and R³ are independently H, halogen, C₁-C₆ alkyl or phenyl;        said phenyl group substituted with 0-3 R^(3a);    -   R^(3a) is halogen or COOR⁴;    -   R⁴ is H or C₁-C₆ alkyl; and    -   R⁹ is H or C₁-C₃ alkyl.

In another embodiment, the present disclosure provides a compoundselected from the exemplified examples within the scope of the firstaspect, or a pharmaceutically acceptable salt, tautomer or stereoisomerthereof.

In another embodiment, there is provided a compound selected from anysubset list of compounds within the scope of the first aspect.

In a second aspect, the present disclosure provides a method ofenhancing, stimulating, and/or increasing an immune response in asubject in need thereof, wherein the method comprises administering tothe subject a therapeutically effective amount of a compound of formula(I) or formula (II), or a pharmaceutically acceptable salt thereof.

In a third aspect, the present disclosure provides a method of blockingthe interaction of PD-L1 with PD-1 and/or CD80 in a subject, wherein themethod comprises administering to the subject a therapeuticallyeffective amount of a compound of formula (I) or formula (II) or apharmaceutically acceptable salt thereof.

In a fourth aspect the present disclosure provides a method ofenhancing, stimulating, and/or increasing an immune response in asubject in need thereof, said method comprising administering to thesubject a therapeutically effective amount of a compound of formula (I)or formula (II), or a pharmaceutically acceptable salt thereof. In afirst embodiment of the second aspect the method further comprisesadministering an additional agent prior to, after, or simultaneouslywith the compound of formula (I), compound of formula (I), or apharmaceutically acceptable salt thereof. In a second embodiment theadditional agent is selected from an antimicrobial agent, an antiviralagent, a cytotoxic agent, a TLR7 agonist, a TLR8 agonist, an HDACinhibitor, and an immune response modifier.

In a fifth aspect the present disclosure provides a method of inhibitinggrowth, proliferation, or metastasis of cancer cells in a subject inneed thereof, said method comprising administering to the subject atherapeutically effective amount a compound of formula (I) or formula(II), or a pharmaceutically acceptable salt thereof. In a firstembodiment of the third aspect the cancer is selected from melanoma,renal cell carcinoma, squamous non-small cell lung cancer (NSCLC),non-squamous NSCLC, colorectal cancer, castration-resistant prostatecancer, ovarian cancer, gastric cancer, hepatocellular carcinoma,pancreatic carcinoma, squamous cell carcinoma of the head and neck,carcinomas of the esophagus, gastrointestinal tract and breast, andhematological malignancies.

In a sixth aspect the present disclosure provides a method of treatingan infectious disease in a subject in need thereof, the methodcomprising administering to the subject a therapeutically effectiveamount of a compound of formula (I) or formula (II), or apharmaceutically acceptable salt thereof. In a first embodiment of thefourth aspect the infectious disease is caused by a virus. In a secondembodiment the virus is selected from HIV, Hepatitis A, Hepatitis B,Hepatitis C, herpes viruses, and influenza.

In a seventh aspect the present disclosure provides a method of treatingseptic shock in a subject in need thereof, the method comprisingadministering to the subject a therapeutically effective amount of acompound of formula (I) or formula (II), or a pharmaceuticallyacceptable salt thereof.

In an eighth aspect the present disclosure provides a method of blockingthe interaction of PD-L1 with PD-1 and/or CD80 in a subject, said methodcomprising administering to the subject a therapeutically effectiveamount of a compound of formula (I) or formula (II), or apharmaceutically acceptable salt thereof.

DETAILED DESCRIPTION

Unless otherwise indicated, any atom with unsatisfied valences isassumed to have hydrogen atoms sufficient to satisfy the valences.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context dictates otherwise.

As used herein, the term “or” is a logical disjunction (i.e., and/or)and does not indicate an exclusive disjunction unless expresslyindicated such as with the terms “either,” “unless,” “alternatively,”and words of similar effect.

The term “alkyl” as used herein, refers to both branched andstraight-chain saturated aliphatic hydrocarbon groups containing, forexample, from 1 to 12 carbon atoms, from 1 to 6 carbon atoms, and from 1to 4 carbon atoms. Examples of alkyl groups include, but are not limitedto, methyl (Me), ethyl (Et), propyl (e.g., n-propyl and i-propyl), butyl(e.g., n-butyl, i-butyl, sec-butyl, and t-butyl), and pentyl (e.g.,n-pentyl, isopentyl, neopentyl), n-hexyl, 2-methylpentyl, 2-ethylbutyl,3-methylpentyl, and 4-methylpentyl. When numbers appear in a subscriptafter the symbol “C”, the subscript defines with more specificity thenumber of carbon atoms that a particular group may contain. For example,“C₁₋₄ alkyl” denotes straight and branched chain alkyl groups with oneto four carbon atoms.

The term “aryl” as used herein, refers to a group of atoms derived froma molecule containing aromatic ring(s) by removing one hydrogen that isbonded to the aromatic ring(s). Representative examples of aryl groupsinclude, but are not limited to, phenyl and naphthyl. The aryl ring maybe unsubstituted or may contain one or more substituents as valenceallows.

The term “haloalkyl” which includes the term “fluoroalkyl” as usedherein is intended to include both branched and straight-chain saturatedaliphatic hydrocarbon groups substituted with one or more fluorineatoms. For example, “C₁₋₄ fluoroalkyl” is intended to include C₁, C₂,C₃, and C₄ alkyl groups substituted with one or more fluorine atoms.Representative examples of fluoroalkyl groups include, but are notlimited to, —CF₃ and —CH₂CF₃.

The terms “halo” and “halogen”, as used herein, refer to F, Cl, Br, orI.

As used herein, the phrase “or a pharmaceutically acceptable saltthereof” refers to at least one compound, or at least one salt of thecompound, or a combination thereof. For example, “a compound of Formula(I) or a pharmaceutically acceptable salt thereof” includes, but is notlimited to, a compound of Formula (I), two compounds of Formula (I), apharmaceutically acceptable salt of a compound of Formula (I), acompound of Formula (I) and one or more pharmaceutically acceptablesalts of the compound of Formula (I), and two or more pharmaceuticallyacceptable salts of a compound of Formula (I).

An “adverse event” or “AE” as used herein is any unfavorable andgenerally unintended, even undesirable, sign (including an abnormallaboratory finding), symptom, or disease associated with the use of amedical treatment. For example, an adverse event can be associated withactivation of the immune system or expansion of immune system cells(e.g., T cells) in response to a treatment. A medical treatment can haveone or more associated AEs and each AE can have the same or differentlevel of severity. Reference to methods capable of “altering adverseevents” means a treatment regime that decreases the incidence and/orseverity of one or more AEs associated with the use of a differenttreatment regime.

As used herein, “hyperproliferative disease” refers to conditionswherein cell growth is increased over normal levels. For example,hyperproliferative diseases or disorders include malignant diseases(e.g., esophageal cancer, colon cancer, biliary cancer) andnon-malignant diseases (e.g., atherosclerosis, benign hyperplasia, andbenign prostatic hypertrophy).

The term “immune response” refers to the action of, for example,lymphocytes, antigen presenting cells, phagocytic cells, granulocytes,and soluble macromolecules that results in selective damage to,destruction of, or elimination from the human body of invadingpathogens, cells or tissues infected with pathogens, cancerous cells,or, in cases of autoimmunity or pathological inflammation, normal humancells or tissues.

The terms “Programmed Death Ligand 1”, “Programmed Cell Death Ligand 1”,“PD-L1”, “PDL1”, “hPD-L1”, “hPD-LI ”, and “B7-H1” are usedinterchangeably, and include variants, isoforms, species homologs ofhuman PD-L1, and analogs having at least one common epitope with PD-L1.The complete PD-L1 sequence can be found under GENBANK® Accession No.NP_054862.

The terms “Programmed Death 1”, “Programmed Cell Death 1”, “ProteinPD-1”, “PD-1”, “PD1”, “hPD-1” and “hPD-I” are used interchangeably, andinclude variants, isoforms, species homologs of human PD-1, and analogshaving at least one common epitope with PD-1. The complete PD-1 sequencecan be found under GENBANK® Accession No. U64863.

The term “treating” refers to inhibiting the disease, disorder, orcondition, i.e., arresting its development; and (iii) relieving thedisease, disorder, or condition, i.e., causing regression of thedisease, disorder, and/or condition and/or symptoms associated with thedisease, disorder, and/or condition.

The present disclosure is intended to include all isotopes of atomsoccurring in the present compounds. Isotopes include those atoms havingthe same atomic number but different mass numbers. By way of generalexample and without limitation, isotopes of hydrogen include deuteriumand tritium. Isotopes of carbon include ¹³C and ₁₄C.Isotopically-labeled compounds of the disclosure can generally beprepared by conventional techniques known to those skilled in the art orby processes analogous to those described herein, using an appropriateisotopically-labeled reagent in place of the non-labeled reagentotherwise employed. Such compounds can have a variety of potential uses,for example as standards and reagents in determining biologicalactivity. In the case of stable isotopes, such compounds can have thepotential to favorably modify biological, pharmacological, orpharmacokinetic properties.

An additional aspect of the subject matter described herein is the useof the disclosed compounds as radiolabeled ligands for development ofligand binding assays or for monitoring of in vivo adsorption,metabolism, distribution, receptor binding or occupancy, or compounddisposition. For example, a macrocyclic compound described herein can beprepared using a radioactive isotope and the resulting radiolabeledcompound can be used to develop a binding assay or for metabolismstudies. Alternatively, and for the same purpose, a macrocyclic compounddescribed herein can be converted to a radiolabeled form by catalytictritiation using methods known to those skilled in the art.

The macrocyclic compounds of the present disclosure can also be used asPET imaging agents by adding a radioactive tracer using methods known tothose skilled in the art.

Those of ordinary skill in the art are aware that an amino acid includesa compound represented by the general structure:

where R and R′ are as discussed herein. Unless otherwise indicated, theterm “amino acid” as employed herein, alone or as part of another group,includes, without limitation, an amino group and a carboxyl group linkedto the same carbon, referred to as “α” carbon, where R and/or R′ can bea natural or an un-natural side chain, including hydrogen. The absolute“S” configuration at the “α” carbon is commonly referred to as the “L”or “natural” configuration. In the case where both the “R” and the“R′”(prime) substituents equal hydrogen, the amino acid is glycine andis not chiral.

Where not specifically designated, the amino acids described herein canbe D- or L-stereochemistry and can be substituted as described elsewherein the disclosure. It should be understood that when stereochemistry isnot specified, the present disclosure encompasses all stereochemicalisomeric forms, or mixtures thereof, which possess the ability toinhibit the interaction between PD-1 and PD-L1 and/or CD80 and PD-L1.Individual stereoisomers of compounds can be prepared synthetically fromcommercially available starting materials which contain chiral centersor by preparation of mixtures of enantiomeric products followed byseparation such as conversion to a mixture of diastereomers followed byseparation or recrystallization, chromatographic techniques, or directseparation of enantiomers on chiral chromatographic columns. Startingcompounds of particular stereochemistry are either commerciallyavailable or can be made and resolved by techniques known in the art.

Certain compounds of the present disclosure can exist in differentstable conformational forms which may be separable. Torsional asymmetrydue to restricted rotation about an asymmetric single bond, for examplebecause of steric hindrance or ring strain, may permit separation ofdifferent conformers. The present disclosure includes eachconformational isomer of these compounds and mixtures thereof.

Certain compounds of the present disclosure can exist as tautomers,which are compounds produced by the phenomenon where a proton of amolecule shifts to a different atom within that molecule. The term“tautomer” also refers to one of two or more structural isomers thatexist in equilibrium and are readily converted from one isomer toanother. All tautomers of the compounds described herein are includedwithin the present disclosure.

The pharmaceutical compounds of the disclosure can include one or morepharmaceutically acceptable salts. A “pharmaceutically acceptable salt”refers to a salt that retains the desired biological activity of theparent compound and does not impart any undesired toxicological effects(see e.g., Berge, S. M. et al., J. Pharm. Sci., 66:1-19 (1977)). Thesalts can be obtained during the final isolation and purification of thecompounds described herein, or separately be reacting a free basefunction of the compound with a suitable acid or by reacting an acidicgroup of the compound with a suitable base. Acid addition salts includethose derived from nontoxic inorganic acids, such as hydrochloric,nitric, phosphoric, sulfuric, hydrobromic, hydroiodic, phosphorous andthe like, as well as from nontoxic organic acids such as aliphatic mono-and dicarboxylic acids, phenyl-substituted alkanoic acids, hydroxyalkanoic acids, aromatic acids, aliphatic and aromatic sulfonic acidsand the like. Base addition salts include those derived from alkalineearth metals, such as sodium, potassium, magnesium, calcium and thelike, as well as from nontoxic organic amines, such asN,N′-dibenzylethylenediamine, N-methylglucamine, chloroprocaine,choline, diethanolamine, ethylenediamine, procaine and the like.

Administration of a therapeutic agent described herein includes, withoutlimitation, administration of a therapeutically effective amount oftherapeutic agent. The term “therapeutically effective amount” as usedherein refers, without limitation, to an amount of a therapeutic agentto treat a condition treatable by administration of a compositioncomprising the PD-1/PD-L1 binding inhibitors described herein. Thatamount is the amount sufficient to exhibit a detectable therapeutic orameliorative effect. The effect can include, for example and withoutlimitation, treatment of the conditions listed herein. The preciseeffective amount for a subject will depend upon the subject's size andhealth, the nature and extent of the condition being treated,recommendations of the treating physician, and therapeutics orcombination of therapeutics selected for administration. Thus, it is notuseful to specify an exact effective amount in advance.

In another aspect, the disclosure pertains to methods of inhibitinggrowth of tumor cells in a subject using the macrocyclic compounds ofthe present disclosure. As demonstrated herein, the compounds of thepresent disclosure are capable of binding to PD-L1, disrupting theinteraction between PD-L1 and PD-1, competing with the binding of PD-L1with anti-PD-1 monoclonal antibodies that are known to block theinteraction with PD-1, enhancing CMV-specific T cell IFNγ secretion, andenhancing HIV-specific T cell IFNγ secretion. As a result, the compoundsof the present disclosure are useful for modifying an immune response,treating diseases such as cancer or infectious disease, stimulating aprotective autoimmune response or to stimulate antigen-specific immuneresponses (e.g., by co-administration of PD-L1 blocking compounds withan antigen of interest).

Pharmaceutical Compositions

In another aspect, the present disclosure provides a composition, e.g.,a pharmaceutical composition, containing one or a combination of thecompounds described within the present disclosure, formulated togetherwith a pharmaceutically acceptable carrier. Pharmaceutical compositionsof the disclosure also can be administered in combination therapy, i.e.,combined with other agents. For example, the combination therapy caninclude a macrocyclic compound combined with at least one otheranti-inflammatory or immunosuppressant agent. Examples of therapeuticagents that can be used in combination therapy are described in greaterdetail below in the section on uses of the compounds of the disclosure.

As used herein, “pharmaceutically acceptable carrier” includes any andall solvents, dispersion media, coatings, antibacterial and antifungalagents, isotonic and absorption delaying agents, and the like that arephysiologically compatible. In some embodiments, the carrier is suitablefor intravenous, intramuscular, subcutaneous, parenteral, spinal orepidermal administration (e.g., by injection or infusion). Depending onthe route of administration, the active compound can be coated in amaterial to protect the compound from the action of acids and othernatural conditions that can inactivate the compound.

A pharmaceutical composition of the disclosure also can include apharmaceutically acceptable anti-oxidant. Examples of pharmaceuticallyacceptable antioxidants include: (1) water soluble antioxidants, such asascorbic acid, cysteine hydrochloride, sodium bisulfate, sodiummetabisulfite, sodium sulfite and the like; (2) oil-solubleantioxidants, such as ascorbyl palmitate, butylated hydroxyanisole(BHA), butylated hydroxytoluene (BHT), lecithin, propyl gallate,alpha-tocopherol, and the like; and (3) metal chelating agents, such ascitric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol, tartaricacid, phosphoric acid, and the like.

The pharmaceutical compositions of the present disclosure can beadministered via one or more routes of administration using one or moreof a variety of methods known in the art. As will be appreciated by theskilled artisan, the route and/or mode of administration will varydepending upon the desired results. In some embodiments, the routes ofadministration for macrocyclic compounds of the disclosure includeintravenous, intramuscular, intradermal, intraperitoneal, subcutaneous,spinal or other parenteral routes of administration, for example byinjection or infusion. The phrase “parenteral administration” as usedherein means modes of administration other than enteral and topicaladministration, usually by injection, and includes, without limitation,intravenous, intramuscular, intraarterial, intrathecal, intracapsular,intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal,subcutaneous, subcuticular, intraarticular, subcapsular, subarachnoid,intraspinal, epidural and intrasternal injection and infusion.

Sterile injectable solutions can be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed bysterilization microfiltration. Generally, dispersions are prepared byincorporating the active compound into a sterile vehicle that contains abasic dispersion medium and the required other ingredients from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, some methods of preparation are vacuumdrying and freeze-drying (lyophilization) that yield a powder of theactive ingredient plus any additional desired ingredient from apreviously sterile-filtered solution thereof.

Examples of suitable aqueous and non-aqueous carriers that can beemployed in the pharmaceutical compositions of the disclosure includewater, ethanol, polyols (such as glycerol, propylene glycol,polyethylene glycol, and the like), and suitable mixtures thereof,vegetable oils, such as olive oil, and injectable organic esters, suchas ethyl oleate. Proper fluidity can be maintained, for example, by theuse of coating materials, such as lecithin, by the maintenance of therequired particle size in the case of dispersions, and by the use ofsurfactants.

These compositions can also contain adjuvants such as preservatives,wetting agents, emulsifying agents and dispersing agents. Prevention ofpresence of microorganisms can be ensured both by sterilizationprocedures, supra, and by the inclusion of various antibacterial andantifungal agents, for example, paraben, chlorobutanol, phenol sorbicacid, and the like. It can also be desirable to include isotonic agents,such as sugars, sodium chloride, and the like into the compositions. Inaddition, prolonged absorption of the injectable pharmaceutical form canbe brought about by the inclusion of agents which delay absorption suchas aluminum monostearate and gelatin.

Pharmaceutically acceptable carriers include sterile aqueous solutionsor dispersions and sterile powders for the extemporaneous preparation ofsterile injectable solutions or dispersion. The use of such media andagents for pharmaceutically active substances is known in the art.Except insofar as any conventional media or agent is incompatible withthe active compound, use thereof in the pharmaceutical compositions ofthe disclosure is contemplated. Supplementary active compounds can alsobe incorporated into the compositions.

Therapeutic compositions typically must be sterile and stable under theconditions of manufacture and storage. The composition can be formulatedas a solution, microemulsion, liposome, or other ordered structuresuitable to high drug concentration. The carrier can be a solvent ordispersion medium containing, for example, water, ethanol, polyol (forexample, glycerol, propylene glycol, and liquid polyethylene glycol, andthe like), and suitable mixtures thereof. The proper fluidity can bemaintained, for example, by the use of a coating such as lecithin, bythe maintenance of the required particle size in the case of dispersionand by the use of surfactants. In many cases, it will be desirable toinclude isotonic agents, for example, sugars, polyalcohols such asmannitol, sorbitol, or sodium chloride in the composition. Prolongedabsorption of the injectable compositions can be brought about byincluding in the composition an agent that delays absorption, forexample, monostearate salts and gelatin.

Alternatively, the compounds of the disclosure can be administered via anon-parenteral route, such as a topical, epidermal or mucosal route ofadministration, for example, intranasally, orally, vaginally, rectally,sublingually or topically.

Any pharmaceutical composition contemplated herein can, for example, bedelivered orally via any acceptable and suitable oral preparation.Exemplary oral preparations include, but are not limited to, forexample, tablets, troches, lozenges, aqueous and oily suspensions,dispersible powders or granules, emulsions, hard and soft capsules,liquid capsules, syrups, and elixirs. Pharmaceutical compositionsintended for oral administration can be prepared according to anymethods known in the art for manufacturing pharmaceutical compositionsintended for oral administration. In order to provide pharmaceuticallypalatable preparations, a pharmaceutical composition in accordance withthe disclosure can contain at least one agent selected from sweeteningagents, flavoring agents, coloring agents, demulcents, antioxidants, andpreserving agents.

A tablet can, for example, be prepared by admixing at least one compoundof Formula (I) and/or at least one pharmaceutically acceptable saltthereof with at least one non-toxic pharmaceutically acceptableexcipient suitable for the manufacture of tablets. Exemplary excipientsinclude, but are not limited to, for example, inert diluents, such as,for example, calcium carbonate, sodium carbonate, lactose, calciumphosphate, and sodium phosphate; granulating and disintegrating agents,such as, for example, microcrystalline cellulose, sodiumcrosscarmellose, corn starch, and alginic acid; binding agents such as,for example, starch, gelatin, polyvinyl-pyrrolidone, and acacia; andlubricating agents, such as, for example, magnesium stearate, stearicacid, and talc. Additionally, a tablet can either be uncoated, or coatedby known techniques to either mask the bad taste of an unpleasanttasting drug, or delay disintegration and absorption of the activeingredient in the gastrointestinal tract thereby sustaining the effectsof the active ingredient for a longer period. Exemplary water solubletaste masking materials include, but are not limited to,hydroxypropyl-methylcellulose and hydroxypropyl-cellulose. Exemplarytime delay materials include, but are not limited to, ethyl celluloseand cellulose acetate butyrate.

Hard gelatin capsules can, for example, be prepared by mixing at leastone compound of Formula (I) and/or at least one salt thereof with atleast one inert solid diluent, such as, for example, calcium carbonate;calcium phosphate; and kaolin.

Soft gelatin capsules can, for example, be prepared by mixing at leastone compound of Formula (I) and/or at least one pharmaceuticallyacceptable salt thereof with at least one water soluble carrier, suchas, for example, polyethylene glycol; and at least one oil medium, suchas, for example, peanut oil, liquid paraffin, and olive oil.

An aqueous suspension can be prepared, for example, by admixing at leastone compound of Formula (I) and/or at least one pharmaceuticallyacceptable salt thereof with at least one excipient suitable for themanufacture of an aqueous suspension, include, but are not limited to,for example, suspending agents, such as, for example, sodiumcarboxymethylcellulose, methylcellulose, hydroxypropylmethyl-cellulose,sodium alginate, alginic acid, polyvinyl-pyrrolidone, gum tragacanth,and gum acacia; dispersing or wetting agents, such as, for example, anaturally-occurring phosphatide, e.g., lecithin; condensation productsof alkylene oxide with fatty acids, such as, for example,polyoxyethylene stearate; condensation products of ethylene oxide withlong chain aliphatic alcohols, such as, for example,heptadecathylene-oxycetanol; condensation products of ethylene oxidewith partial esters derived from fatty acids and hexitol, such as, forexample, polyoxyethylene sorbitol monooleate; and condensation productsof ethylene oxide with partial esters derived from fatty acids andhexitol anhydrides, such as, for example, polyethylene sorbitanmonooleate. An aqueous suspension can also contain at least onepreservative, such as, for example, ethyl and n-propylp-hydroxybenzoate; at least one coloring agent; at least one flavoringagent; and/or at least one sweetening agent, including but not limitedto, for example, sucrose, saccharin, and aspartame.

Oily suspensions can, for example, be prepared by suspending at leastone compound of Formula (I) and/or at least one pharmaceuticallyacceptable salt thereof in either a vegetable oil, such as, for example,arachis oil, sesame oil, and coconut oil; or in mineral oil, such as,for example, liquid paraffin. An oily suspension can also contain atleast one thickening agent, such as, for example, beeswax, hardparaffin, and cetyl alcohol. In order to provide a palatable oilysuspension, at least one of the sweetening agents already describedherein above, and/or at least one flavoring agent can be added to theoily suspension. An oily suspension can further contain at least onepreservative, including, but not limited to, for example, ananti-oxidant, such as, for example, butylated hydroxyanisol, andalpha-tocopherol.

Dispersible powders and granules can, for example, be prepared byadmixing at least one compound of Formula (I) and/or at least onepharmaceutically acceptable salt thereof with at least one dispersingand/or wetting agent, at least one suspending agent, and/or at least onepreservative. Suitable dispersing agents, wetting agents, and suspendingagents are already described above. Exemplary preservatives include, butare not limited to, for example, anti-oxidants, e.g., ascorbic acid. Inaddition, dispersible powders and granules can also contain at least oneexcipient, including, but not limited to, for example, sweeteningagents, flavoring agents, and coloring agents.

An emulsion of at least one compound of Formula (I) and/or at least onepharmaceutically acceptable salt thereof can, for example, be preparedas an oil-in-water emulsion. The oily phase of the emulsions comprisingthe compounds of Formula (I) can be constituted from known ingredientsin a known manner. The oil phase can be provided by, but is not limitedto, for example, a vegetable oil, such as, for example, olive oil andarachis oil; a mineral oil, such as, for example, liquid paraffin; andmixtures thereof. While the phase can comprise merely an emulsifier, itcan comprise a mixture of at least none emulsifier with a fat or an oilor with both a fat and an oil. Suitable emulsifying agents include, butare not limited to, for example, naturally-occurring phosphatides, e.g.,soy bean lecithin, esters or partial esters derived from fatty acids andhexitol anhydrides, such as, for example sorbitan monoleate, andcondensation products of partial esters with ethylene oxide, such as,for example, polyoxyethylene sorbitan monooleate. In some embodiments, ahydrophilic emulsifier is included together with a lipophilic emulsifierwhich acts as a stabilizer. It is also sometimes desirable to includeboth an oil and a fat. Together, the emulsifier(s) with or withoutstabilizer(s) make up the so-called emulsifying wax, and the waxtogether with the oil and fat make up the so-called emulsifying ointmentbase which forms the oily dispersed phase of the cream formulations. Anemulsion can also contain a sweetening agent, a flavoring agent, apreservative, and/or an antioxidant. Emulsifiers and emulsionstabilizers suitable for use in the formulation of the presentdisclosure include Tween 60, Span 80, cetostearyl alcohol, myristylalcohol, glyceryl monostearate, sodium lauryl sulfate, glyceraldisterate alone or with a wax, or other materials well known in the art.

The active compounds can be prepared with carriers that will protect thecompound against rapid release, such as a controlled releaseformulation, including implants, transdermal patches, andmicroencapsulated delivery systems. Biodegradable, biocompatiblepolymers can be used, such as ethylene vinyl acetate, polyanhydrides,polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Manymethods for the preparation of such formulations are patented orgenerally known to those skilled in the art. See, e.g., Robinson, J. R.,ed., Sustained and Controlled Release Drug Delivery Systems, MarcelDekker, Inc., New York (1978).

Therapeutic compositions can be administered with medical devices knownin the art. For example, in one embodiment, a therapeutic composition ofthe disclosure can be administered with a needleless hypodermicinjection device, such as the devices disclosed in U.S. Pat. Nos.5,399,163, 5,383,851, 5,312,335, 5,064,413, 4,941,880, 4,790,824, or4,596,556. Examples of well-known implants and modules useful in thepresent disclosure include: U.S. Pat. No. 4,487,603, which discloses animplantable micro-infusion pump for dispensing medication at acontrolled rate; U.S. Pat. No. 4,486,194, which discloses a therapeuticdevice for administering medication through the skin; U.S. Pat. No.4,447,233, which discloses a medication infusion pump for deliveringmedication at a precise infusion rate; U.S. Pat. No. 4,447,224, whichdiscloses a variable flow implantable infusion apparatus for continuousdrug delivery; U.S. Pat. No. 4,439,196, which discloses an osmotic drugdelivery system having multi-chamber compartments; and U.S. Pat. No.4,475,196, which discloses an osmotic drug delivery system. Thesepatents are incorporated herein by reference. Many other such implants,delivery systems, and modules are known to those skilled in the art.

In certain embodiments, the compounds of the disclosure can beformulated to ensure proper distribution in vivo. For example, theblood-brain barrier (BBB) excludes many highly hydrophilic compounds. Toensure that therapeutic compounds of the disclosure cross the BBB (ifdesired), they can be formulated, for example, in liposomes. For methodsof manufacturing liposomes, see, e.g., U.S. Pat. Nos. 4,522,811,5,374,548, and 5,399,331. The liposomes can comprise one or moremoieties which are selectively transported into specific cells ororgans, thus enhance targeted drug delivery (see, e.g., Ranade, V. V.,J. Clin. Pharmacol., 29:685 (1989)). Exemplary targeting moietiesinclude folate or biotin (see, e.g., U.S. Pat. No. 5,416,016 to Low etal.); mannosides (Umezawa et al., Biochem. Biophys. Res. Commun.,153:1038 (1988)); macrocyclic compounds (Bloeman, P. G. et al., FEBSLett., 357:140 (1995); Owais, M. et al., Antimicrob. Agents Chemother.,39:180 (1995)); surfactant protein A receptor (Briscoe et al., Am. J.Physiol., 1233:134 (1995)); p 120 (Schreier et al., J. Biol. Chem.,269:9090 (1994)); see also Keinanen, K. et al., FEBS Lett., 346:123(1994); Killion, J. J. et al., Immunomethods 4:273 (1994).

SYNTHETIC METHODS

The compounds may be made by methods known in the art including thosedescribed below and including variations within the skill of the art.Some reagents and intermediates are known in the art. Other reagents andintermediates can be made by methods known in the art using readilyavailable materials. The variables (e.g. numbered “R” substituents) usedto describe the synthesis of the compounds are intended only toillustrate how to make the compounds and are not to be confused withvariables used in the claims or in other sections of the specification.The following methods are for illustrative purposes and are not intendedto limit the scope of the invention.

Abbreviations used in the schemes generally follow conventions used inthe art. Chemical abbreviations used in the specification and examplesare defined as follows: “THF” for tetrahydrofuran; “DMF” forN,N-dimethylformamide; “MeOH” for methanol; “EtOH” for ethanol; “n-PrOH”for 1-propyl alcohol or propan-1-ol; “i-PrOH” for 2-propyl alcohol orpropan-2-ol; “Ar” for aryl; “TFA” for trifluoroacetic acid; “DMSO” fordimethylsulfoxide; “EtOAc” for ethyl acetate; “Et₂O” for diethyl ether;“DMAP” for 4-dimethylaminopyridine; “DCE” for 1,2-dichloroethane; “ACN”for acetonitrile; “DME” for 1,2-dimethoxyethane; “h” for hours; “rt” forroom temperature or retention time (context will dictate); “min” forminutes; “HOBt” for 1-hydroxybenzotriazole hydrate; “HCTU” for1-[bis(dimethylamino)methylen]-5-chlorobenzotriazolium 3-oxidehexafluorophosphate orN,N,N′,N′-tetramethyl-O-(6-chloro-1H-benzotriazol-1-yl)uroniumhexafluorophosphate; “HATU” for 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo [4,5-b]pyridinium 3-oxid hexafluorophosphate orN-[(dimethylamino)-1H-1,2,3-triazolo-[4,5-b]pyridin-1-ylmethylene]-N-methylmethanaminiumhexafluorophosphate N-oxide; “DIEA” and “iPrNEt₂” fordiisopropylethylamine; “Et₃N” for triethyl amine.

Abbreviations are defined as follows: “1×” for once, “2×” for twice,“3×” for thrice, “° C.” for degrees Celsius, “eq” for equivalent orequivalents, “g” for gram or grams, “mg” for milligram or milligrams,“L” for liter or liters, “mL” for milliliter or milliliters, “μL” formicroliter or microliters, “N” for normal, “M” for molar, “mmol” formillimole or millimoles, “min” for minute or minutes, “h” for hour orhours, “rt” for room temperature, “RT” for retention time, “atm” foratmosphere, “psi” for pounds per square inch, “conc.” for concentrate,“sat” or “sat'd ” for saturated, “MW” for molecular weight, “mp” formelting point, “ee” for enantiomeric excess, “MS” or “Mass Spec” formass spectrometry, “ESI” for electrospray ionization mass spectroscopy,“HR” for high resolution, “HRMS” for high resolution mass spectrometry,“LC” for liquid chromatography, “LCMS” for liquid chromatography massspectrometry, “HPLC” for high pressure liquid chromatography, “RP HPLC”for reverse phase HPLC, “TLC” or “tic” for thin layer chromatography,“NMR” for nuclear magnetic resonance spectroscopy, “¹H” for proton, “δ”for delta, “s” for singlet, “d” for doublet, “t” for triplet, “q” forquartet, “m” for multiplet, “br” for broad, “Hz” for hertz, and “α”,“β”, “R”, “S”, “E”, and “Z” are stereochemical designations familiar toone skilled in the art.

BMT-001's structure is

BMT-002's structure is

General Procedure for the Preparation of the Structures of Claim I:

A solution of BMT-001 or BMT-002 and electrophile in MeOH or EtOH orn-PrOH or i-PrOH was stirred at room temperature to 100° C. for 0.5-48hours. After all the solvents were removed under vacuum, the residue waspurified by the preparative HPLC to give the compounds of Claim I.

Compound 1001

Agents Used Starting Material BMT-001 Electrophile3,4-Dimethoxycyclobut-3-ene-1,2-dione MS MS (M/2 + H)⁺ Calcd. 1054 MS(M/2 + H)⁺ Observ. 1054 Retention Time 1.55 min LC Condition Solvent A5:95 acetonitrile:water with 10 mM ammonium acetate Solvent B 95:5acetonitrile:water with 10 mM ammonium acetate Start % B   0 Final % B 100 Gradient Time   3 min Flow Rate   1 mL/min Wavelength  220Temperature  50° C. Column Waters Acquity UPLC BEH C18, 2.1 × 50 mm,1.7-μm particles

Compound 1002

Agents Used Starting Material BMT-001 Electrophile3,4-Dimethoxycyclobut-3-ene-1,2-dione MS MS (M/2 + H)⁺ Calcd. 999 MS(M/2 + H)⁺ Observ. 999 Retention Time 1.66 min LC Condition Solvent A5:95 acetonitrile:water with 10 mM ammonium acetate Solvent B 95:5acetonitrile:water with 10 mM ammonium acetate Start % B  0 Final % B100 Gradient Time  3 min Flow Rate  1 mL/min Wavelength 220 Temperature 50° C. Column Waters Acquity UPLC BEH C18, 2.1 × 50 mm, 1.7-μmparticles

Compound 1003

Agents Used Starting Material BMT-001 Electrophile3,4-Dimethoxycyclobut-3-ene-1,2-dione MS MS (M/2 + H)⁺ Calcd. 1082 MS(M/2 + H)⁺ Observ. 1082 Retention Time 1.92 min LC Condition Solvent A5:95 acetonitrile:water with 10 mM ammonium acetate Solvent B 95:5acetonitrile:water with 10 mM ammonium acetate Start % B   0 Final % B 100 Gradient Time   3 min Flow Rate 0.75 mL/min Wavelength  220Temperature  70° C. Column Waters XBridge C18, 2.1 mm × 50 mm, 1.7 μmparticles

Compound 1004

Agents Used Starting Material BMT-001 Electrophile3-(Dimethylamino)-4-methoxycyelobut-3-ene-1,2-dione MS MS (M/2 + H)⁺Calcd. 1067 MS (M/2 + H)⁺ Observ. 1067 Retention Time 1.48 min LCCondition Solvent A 5:95 acetonitrile:water with 10 mM ammonium acetateSolvent B 95:5 acetonitrile:water with 10 mM ammonium acetate Start % B  0 Final % B  100 Gradient Time 3 min Flow Rate   1 mL/min Wavelength 220 Temperature  50° C. Column Waters XBridge C18, 2.1 mm × 50 mm, 1.7μm particles

Compound 1005

Agents Used Starting Material BMT-001 Electrophile Ethyl4-((2-ethoxy-3,4-dioxocyclobut-1-en-1-yl)amino)benzoate MS MS (M/2 + H)⁺Calcd. 1187 MS (M/2 + H)⁺ Observ. 1187 Retention Time 1.91 min LCCondition Solvent A 5:95 acetonitrile:water with 10 mM ammonium acetateSolvent B 95:5 acetonitrile:water with 10 mM ammonium acetate Start % B  0 Final % B  100 Gradient Time   3 min Flow Rate   1 mL/min Wavelength 220 Temperature  50 °C Column Waters XBridge C18, 2.1 mm × 50 mm, 1.7μm particles

Compound 1006

Agents Used Starting Material BMT-001 Electrophile3-((2,6-Dichlorophenyl)amino)-4-methoxycyclobut-3-ene-1,2-dione MS MS(M/2 + H)⁺ Calcd. 1183 MS (M/2 + H)⁺ Observ. 1183 Retention Time 1.82min LC Condition Solvent A 5:95 acetonitrile:water with 10 mM ammoniumacetate Solvent B 95:5 acetonitrile:water with 10 mM ammonium acetateStart % B   0 Final % B  100 Gradient Time   3 min Flow Rate 0.75 mL/minWavelength  220 Temperature  70° C. Column Waters BEH C18, 2.1 × 50 mm,1.7-μm particlesparticles

Compound 1007

Agents Used Starting Material BMT-001 Electrophile3,4-Diisopropoxycyclobut-3-ene-1,2-dione MS MS (M/2 + H)⁺ Calcd. 1082 MS(M/2 + H)⁺ Observ. 1082 Retention Time 1.48 min LC Condition Solvent A5% ACN:95% Water:10 mM Ammonium Actetate Solvent B 95% ACN:5% Water:10mM Ammonium Actetate Start % B   0 Final % B  100 Gradient Time   2 minFlow Rate   1 mL/min Wavelength  220 Temperature  40° C. ColumnPhenomenex LUNA C18, 30 × 2, 3u

Compound 1008

Agents Used Starting Material BMT-001 Electrophile3,4-Diisopropoxycyclobut-3-ene-1,2-dione MS MS (M/2 + H)⁺ Calcd. 1013 MS(M/2 + H)⁺ Observ. 1013 Retention Time 1.66 min LC Condition Solvent A5:95 acetonitrile:water with 10 mM ammonium acetate Solvent B 95:5acetonitrile:water with 10 mM ammonium acetate Start % B   0 Final % B 100 Gradient Time   3 min Flow Rate   1 mL/min Wavelength  220Temperature  50° C. Column Waters XBridge C18, 2.1 mm × 50 mm, 1.7 μmparticles

Compound 1009

Agents Used Starting Material BMT-001 Electrophile4-((2-Ethoxy-3,4-dioxocyclobut-1-en-1-yl)amino)benzoic acid MS MS (M/2 +H)⁺ Calcd. 1159 MS (M/2 + H)⁺ Observ. 1159 Retention Time 1.28 min LCCondition Solvent A 5% ACN:95% Water:10 mM Ammonium Actetate Solvent B95% ACN:5% Water:10 mM Ammonium Actetate Start % B   0 Final % B  100Gradient Time   2 min Flow Rate   1 mL/min Wavelength  220 Temperature 40° C. Column Phenomenex LUNA C18, 30 × 2, 3u

Biological Activity

The ability of the compounds of formula (I) to bind to PD-L1 wasinvestigated using a PD-1/PD-L1 Homogenous Time-Resolved Fluorescence(HTRF) binding assay.

Homogenous Time-Resolved Fluorescence (HTRF) Binding Assay

The interaction of PD-1 and PD-L1 can be assessed using soluble,purified preparations of the extracellular domains of the two proteins.The PD-1 and PD-L1 protein extracellular domains were expressed asfusion proteins with detection tags, for PD-1, the tag was the Fcportion of Immunoglobulin (PD-1-Ig) and for PD-L1 it was the 6 histidinemotif (PD-L1-His). All binding studies were performed in an HTRF assaybuffer consisting of dPBS supplemented with 0.1% (with) bovine serumalbumin and 0.05% (v/v) Tween-20. For the h/PD-L1-His binding assay,inhibitors were pre-incubated with PD-L1-His (10 nM final) for 15 m in 4μl of assay buffer, followed by addition of PD-1-Ig (20 nM final) in 1μl of assay buffer and further incubation for 15 m. HTRF detection wasachieved using europium crypate-labeled anti-Ig (1 nM final) andallophycocyanin (APC) labeled anti-His (20 nM final). Antibodies werediluted in HTRF detection buffer and 5 μl was dispensed on top of thebinding reaction. The reaction mixture was allowed to equilibrate for 30minutes and the resulting signal (665 nm/620 nm ratio) was obtainedusing an EnVision fluorometer. Additional binding assays wereestablished between the human proteins PD-1-Ig/PD-L2-His (20 & 5 nM,respectively) and CD80-His/PD-L1-Ig (100 & 10 nM, respectively).

Recombinant Proteins: Human PD-1 (25-167) with a C-terminal human Fcdomain of immunoglobulin G (Ig) epitope tag [hPD-1 (25-167)-3S-IG] andhuman PD-L1 (18-239) with a C-terminal His epitope tag[hPD-L1(18-239)-TVMV-His] were expressed in HEK293T cells and purifiedsequentially by ProteinA affinity chromatography and size exclusionchromatography. Human PD-L2-His and CD80-His was obtained throughcommercial sources.

Table 1 lists the IC₅₀ values for representative examples of thisdisclosure measured in the PD-1/PD-L1 Homogenous Time-ResolvedFluorescence (HTRF) binding assay.

TABLE 1 Ex Number HTRF IC₅₀ (μM) 1001 0.0042 1002 0.0036 1003 0.016 10040.0043 1005 0.0014 1006 0.0028 1007 0.0016 1008 n/a 1009 0.0029

The compunds of formula (I) possess activity as inhibitors of thePD-1/PD-L1 interaction, and therefore, can be used in the treatment ofdiseases or deficiencies associated with the PD-1/PD-L1 interaction. Viainhibition of the PD-1/PD-L1 interaction, the compounds of the presentdisclosure can be employed to treat infectious diseases such as HIV,septic shock, Hepatitis A, B, C, or D and cancer.

It is to be appreciated that the Detailed Description section, and notthe Summary and Abstract sections, is intended to be used to interpretthe claims. The Summary and Abstract sections can set forth one or morebut not all exemplary embodiments of the present disclosure ascontemplated by the inventor(s), and thus, are not intended to limit thepresent disclosure and the appended claims in any way.

The present disclosure has been described above with the aid offunctional building blocks illustrating the implementation of specifiedfunctions and relationships thereof. The boundaries of these functionalbuilding blocks have been arbitrarily defined herein for the convenienceof the description. Alternate boundaries can be defined so long as thespecified functions and relationships thereof are appropriatelyperformed.

The foregoing description of the specific embodiments will so fullyreveal the general nature of the disclosure that others can, by applyingknowledge within the skill of the art, readily modify and/or adapt forvarious applications such specific embodiments, without undueexperimentation, without departing from the general concept of thepresent disclosure. Therefore, such adaptations and modifications areintended to be within the meaning and range of equivalents of thedisclosed embodiments, based on the teaching and guidance presentedherein. It is to be understood that the phraseology or terminologyherein is for the purpose of description and not of limitation, suchthat the terminology or phraseology of the present specification is tobe interpreted by the skilled artisan in light of the teachings andguidance.

The breadth and scope of the present disclosure should not be limited byany of the above-described exemplary embodiments, but should be definedonly in accordance with the following claims and their equivalents.

What is claimed is:
 1. A compound of formula (I)

or a pharmaceutically acceptable salt thereof, wherein: R^(x) and R^(y)are independently H,

provided that at least one of R^(x) and R^(y) is other than H; R¹ is H,halogen or C₁-C₆ alkyl; R² and R³ are independently H, halogen, C₁-C₆alkyl, or aryl; said aryl group substituted with 0-3 R^(3a); R^(3a) ishalogen or COOR⁴; R⁴ is H or C₁-C₆ alkyl; and R⁹ is H or C₁-C₃ alkyl. 2.The compound of claim 1 wherein R² and R³ are independently H, halogen,C₁-C₆ alkyl or phenyl; said phenyl group substituted with 0-3 R^(3a);R^(3a) is halogen or COOR⁴; R⁴ is H or C₁-C₆ alkyl; and R⁹ is H or C₁-C₃alkyl.
 3. The compound of claim 1, or a pharmaceutically acceptable saltthereof, wherein R^(x) is H.
 4. The compound of claim 1, or apharmaceutically acceptable salt thereof, wherein R^(y) is H.
 5. Thecompound of claim 1, or a pharmaceutically acceptable salt thereof,wherein R⁹ is H or —CH₃.
 6. A pharmaceutical composition comprising acompound of any of claims 1 to 5, or a pharmaceutically acceptable saltthereof, and a pharmaceutically acceptable carrier.
 7. A method ofenhancing, stimulating, and/or increasing an immune response in asubject in need thereof, said method comprising administering to thesubject a therapeutically effective amount of a compound of any one ofclaims 1 to 5, or a therapeutically acceptable salt thereof.
 8. A methodof inhibiting growth, proliferation, or metastasis of cancer cells in asubject in need thereof, said method comprising administering to thesubject a therapeutically effective amount of a compound of any one ofclaims 1 to 5, or a therapeutically acceptable salt thereof.
 9. Themethod of claim 8, wherein the cancer is selected from melanoma, renalcell carcinoma, squamous non-small cell lung cancer (NSCLC),non-squamous NSCLC, colorectal cancer, castration-resistant prostatecancer, ovarian cancer, gastric cancer, hepatocellular carcinoma,pancreatic carcinoma, squamous cell carcinoma of the head and neck,carcinomas of the esophagus, gastrointestinal tract and breast, andhematological malignancies.
 10. A method of treating an infectiousdisease in a subject in need thereof, the method comprisingadministering to the subject a therapeutically effective amount of acompound of any one of claims 1 to 5, or a therapeutically acceptablesalt thereof.
 11. The method of claim 10, wherein the infectious diseaseis caused by a virus.
 12. A method of treating septic shock in a subjectin need thereof, the method comprising administering to the subject atherapeutically effective amount of a compound of any one of claims 1 to5, or a therapeutically acceptable salt thereof.
 13. A method forblocking the interaction of PD-L1 with PD-1 and/or CD80 in a subject,said method comprising administering to the subject a therapeuticallyeffective amount of a compound of any one of claims 1 to 5, or atherapeutically acceptable salt thereof.